dw dialer -> Home ->Whatsapp -> Whatsapp shows -> home -> dw dialer -> home -> whatsapp =>dialer shows
dw dialer -> back -> Whatsapp => Ok , whatsapp shows
Latest version , both phones Xperia X & HTC 10
looks like dw dialer stays in the background , when Whatsapp starts
it's activating the dw dialer.
** Happens only after the latest Android update (7.0)